Field of Application
The present invention relates to an electric power converter apparatus incorporating switching elements, which performs electric power conversion by switching operation of the switching elements.
Description of Related Art
Types of electric power converter apparatus are known, such as an electric power source apparatus disclosed in Japanese patent publication No. 2009-100515 (designated in the following as reference 1), in which switching elements of a plurality of electric power converter circuits are switched to perform electric power conversion, under control of respective control circuits, with respective output currents from the electric power converter circuits being combined to constitute the output current from the apparatus.
The electric power source apparatus of reference 1 incorporates three DC-DC converters and three controllers (control circuits). Each DC-DC converter incorporates switching elements, and executes switching of the switching elements to perform conversion of electric power that is supplied to input terminals, and supplies converted electric power from output terminals. Each controller generates a PWM (pulse width modulation) signal for controlling the switching elements of a corresponding one of the DC-DC converters. The phases of the PWM signals from the three DC-DC converters are evenly dispersed, thereby evenly dispersing the phase of a ripple current (produced as a result of the switching of the switching elements) in the output current from the electric power source apparatus. The objective of this is to reduce the amplitude of the ripple current.
However with that method, although the amplitude of the ripple current can be reduced, there is no reduction in amplitude of ripple current frequency components, i.e., components at frequencies which are harmonics of the ripple current frequency. As a result, substantial electrical noise may be produced by the output current from such an electric power converter apparatus, at frequencies which are sufficiently high to cause interference with radio reception.